In some special cases, when an artificial component is needed to be fitted at a knee joint of a human body, the femoral condyle must be cut and shaped such that the femoral condyle will have a special dimension and shape to cooperate with a corresponding artificial component.
At present, in the operation of Total Knee Arthroplasty, it tends to take a very long time for an orthopedic surgeon to assure that the knee joint is well fitted and balanced. A proper ligament tension can be achieved when the balanced knee joint has a correct desired angle between the mechanical axis and the anatomic axis of the knee. This is very important for the entire motion of the knee joint. Thus, a more natural and effective artificial component of the knee joint and the wear resistance characteristics of the artificial component can be provided. The correct dimensions of the artificial component are also a very important factor, which will bring the operation into success or otherwise failure. If a wrong component is selected, or some dimension errors of the artificial component are formed, the associated soft tissue may become too tight or too loose, thus arousing a very poor usage performance of the artificial component.
An instrument for orthopedic surgical operation has been disclosed in a Chinese invention patent application disclosure CN1132067A, the application number of which Chinese invention patent application is 951190946 and the publication date of the same is Oct. 2, 1996. The orthopedic surgical instrument is used in the total knee arthroplasty to determine the dimension of a femur and respective implanted components and provide correct alignment indication and help a surgeon to achieve a proper soft tissue balance for the joint. The use of such an orthopedic surgical instrument can assist a surgeon in selecting dimensions of respective implanted components, determining the cutting amount of a bone on the distal end, providing a correct soft tissue balance and adjusting the instrument for cutting the bone. This known instrument provides a surgeon with several check and verification systems so that the surgeon can check whether the instrument has been correctly adjusted and the joint has been correctly balanced before cutting the femur. This orthopedic surgical instrument comprises a rotary alignment guide which assists a surgeon to determine correct rotary alignment of the knee joint. The correct rotary alignment of the knee joint is made by referring to standard boundary marks of a femur such as posterior condyle and superior condyle. This rotary alignment guide comprises a groove for guiding a saw blade which is used to remove the posterior condyle of the femur.
In summary, in the traditional art, the cutting operation for the femoral condyle is performed in steps, as shown in FIGS. 1-5. The first step is to perform osteotomy at the proximal tibia. Then, a guide is inserted into the femoral medulla, and the anterior portion of the femoral condyle is cut roughly, through which the angle of external rotation of the artificial femoral component can be determined. Subsequently, the osteotomy at the distal femur is performed to find out the valgus angle and the joint line. Then, the dimensions of the femoral component are calculated. After that, the osteotomy at the anterior and posterior condyles of the femur and the osteotomy at the anterior and posterior bevel angles of the femur are performed. The cruciate ligament and the meniscus are removed, and thereafter the flexion gap is measured by means of spacers and the correctness of the osteotomy of the tibia is determined, whether the extension gap is correct is determined by extending the knee, and the whole alignment and the balance status of ligaments are measured. If necessary, the osteotomy of the femur is further performed, the distal femur is repaired, the osteotomy in the intercondylar notch of the femur is performed, and the osteotomy in a bevel angle is performed. Thereafter, a plug hole for the artificial tibial component is chiseled, and the angle of external rotation of the artificial tibial component is determined. Then, the osteotomy of the patella is performed, a fixing hole for the artificial patellar component is bored, and the motion path of the patella is checked.
As shown in FIGS. 1-5, since this traditional method performs the osteotomy at five surfaces of the distal femur in steps, namely, the osteotomy at the front portion of the femoral condyle, the osteotomy at the distal femur, the osteotomy at the anterior and posterior condyles of the femur, and the osteotomy at the anterior and posterior bevel angles of the femur, the disadvantages are as follows: poor accuracies of the angles among the respective bone resected surfaces make it impossible to completely match the cut surfaces with the prosthesis; in addition, the operation scheme is complex, with a lot of operation instruments needed, and the operative process is hard to be controlled, resulting in a long time of the osteotomy. Such an operation often brings great pains to a patient, or even some accidental cases may occur due to a long time operation; a lot of complication diseases may be ensued if the prosthesis is not matched with the bone resected surfaces.
In a U.S. Pat. No. 7,641,662 (Jan. 5, 2010), a femoral condyle cutting and shaping center is provided for shaping a plurality of surfaces at the same time. However, this femoral condyle cutting and shaping center cannot adjust the distances among the respective cutting and shaping tools, so that it is impossible to adjust the cutting shapes and dimensions in the osteotomy according to different patents and achieve the anti-clockwise and clockwise rotatable cutting.